Since it is fully backwards compatible, devices offering UHS-III
bus interface will accept the billions of existing SD memory cards
in the market today.

The UHS-III high-speed interface signals are assigned to the second row of SD memory card pins introduced with UHS-II. This newest bus
transfer speed option will be available in full-size SDHC and SDXC cards, as well as microSDHC and microSDXC cards. It does not change the physical size or shape of the cards as the move from UHS-II to UHS-III involves only a PHY change.